1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device, and more specifically to a heat treatment process for an ion implanted layer or a silicon nitride film layer.
2. Description of the Related Art
Enhancement of the performance of a large-scale integrated circuit (LSI) accompanies enlargement of the degree of the integration. When miniaturized semiconductors are manufactured, each semiconductor layer, dielectric layer, or conductor layer must have desirable properties or must be precisely worked or formed according to the design.
However, since recent semiconductor devices merge a large number of fine elements, they require such a manufacturing method that is designed better and more carefully than before and has high consistency in each process step. From this point of view, the processes for forming source-drain regions and for forming a silicon nitride film (Si3N4) used for sidewalls of a gate electrode in a MOS transistor have had become problems.
In miniaturization of elements, parasitic resistance and short-channel effect in a MOS transistor, etc. increase as the size of the elements is reduced. Therefore, it becomes important that the source-drain regions are made low in electrical resistance and shallow.
Japanese Patent Application Laid-Open No. 2003-309079 discloses a method in which a source-drain diffusion layer is formed by irradiating light from a xenon (Xe) flash lamp under the condition of irradiation time of 10 milliseconds and irradiation energy of 35 J/cm2, down onto the semiconductor substrate where a gate electrode is formed on a silicon oxide film and further implanted with ions.
However, it is difficult to form shallow impurity regions low in electrical resistance without damaging the wafer, because a process window is small in the conventional annealing process using a flash lamp or a laser.
On the other hand, there are also problems with the formation of a silicon nitride film by the conventional processes when one intends to manufacture the recent semiconductor devices with a shallow impurity region.
When a source-drain diffusion layer is formed in the manufacturing process of miniaturized MOSFET, a silicon nitride film plays an important role as a sidewall insulation film of a gate electrode. Conventionally, the gate sidewall silicon nitride film is usually formed in the shape of a film at a high temperature of approximately 700–780° C.
However, under such a thermal budget, the next-generation semiconductor devices advanced in high integration and miniaturization are difficult to be manufactured, because a diffusion layer once activated is inactivated again to make the electrical resistance of the diffusion layer higher, or impurities re-diffuse to generate the short-channel effect, or the like resulting in degradation of element characteristics.
Also known is a method in which a silicon nitride film (HCD-SiN) is formed by a LPCVD process using hexachlorodisilane (Si2Cl6). In this method, since a deposition speed is larger than that of a DCS-SiN film, the deposition can be performed at a lower temperature (550° C. or less). Besides, although the DCS-SiN film can be formed in the shape of a film at a low temperature, productivity is extremely poor due to the small deposition speed.
However, there is a problem with a silicon nitride film formed in the shape of a film at a low temperature that etching rate by a solution containing HF is too large because of high impurity (chlorine, hydrogen) concentration and low density.
Japanese Patent Application Laid-Open No. 2002-118078 discloses a method in which quality of a film such as a silicon nitride film is improved by irradiating white light with energy of 10 to 100 J/cm2 for 10 milliseconds or less onto contact and silicide layers connecting a substrate to the wiring, or a silicon nitride film formed as a sidewall of a gate electrode.
However, there still remain a lot of uninvestigated problems such as occurrence of stress generated by the short time irradiation of light, various defects introduced into a recipient body.
To sum up, in manufacturing the recent miniaturized semiconductor device, there have been the requirements contrary to each other between the formation of a source-drain impurity diffused layer and the formation of a silicon nitride film used as a sidewall of a gate electrode, etc. in a MOS structure, and it has been difficult to cope with them.